Viewpager显示错误的页面

Question

我有一个jake Wharton的viewpagerindicator,在那个viewpager我有6个页面.所有页面都包含listviews,我用AsyncTask加载它们.有时viewpager在错误的索引显示错误的页面.这是我的viewpager适配器:

public class TestFragmentAdapter extends FragmentPagerAdapter{
    protected static final String[] CONTENT = new String[] { "a","b","c","d","e","f" };

    private int mCount = CONTENT.length;
    Fragment fragment1,fragment2,fragment3,fragment4,fragment5,fragment6;

    public TestFragmentAdapter(FragmentManager fm) {
        super(fm);
        fragment1 = new CategoryListView();
        fragment2 = CustomizedListviewRecent.newInstance(41);
        fragment3 = CustomizedListviewMostRecents.newInstance(0);
        fragment4 = CustomizedListviewPopulars.newInstance();
        fragment5 = CustomizedListviewRecent.newInstance(42);
        fragment6 = CustomizedListviewRecent.newInstance(43);

    }

    @Override
    public Fragment getItem(int position) {
        if(position == 0)
            return fragment1;
        else if(position == 1)
            return fragment2;
        else if(position == 2)
            return fragment3;
        else if(position == 3)
            return fragment4;
        else if(position == 4)
            return fragment5;
        else
            return fragment6;
    }
    @Override
    public int getCount() {
        return mCount;
    }

    @Override
    public CharSequence getPageTitle(int position) {
      return TestFragmentAdapter.CONTENT[position % CONTENT.length];
    }

    public void setCount(int count) {
        if (count > 0 && count <= 10) {
            mCount = count;
            notifyDataSetChanged();
        }
    }

}

以下是我创建viewpager的方法:

public class SampleTitlesDefault extends BaseSampleActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mAdapter = new TestFragmentAdapter(getSupportFragmentManager());

        mPager = (ViewPager)findViewById(R.id.pager);
        mPager.setAdapter(mAdapter);

        mIndicator = (TitlePageIndicator)findViewById(R.id.indicator);
        mIndicator.setViewPager(mPager);
        mIndicator.setCurrentItem(1);
    }

}

这可能有什么问题？我该如何解决这个问题？感谢您的帮助

Answer 1

请不要Fragment自己“缓存” s，因为它已经为您做到了这一点。

也就是说，您应该将newInstance它们放在getItem方法内部，而不是在创建适配器时。例子：

public TestFragmentAdapter(FragmentManager fm) {
    super(fm);
}

@Override
public Fragment getItem(int position) {
    if(position == 0)
        return new CategoryListView();
    else if(position == 1)
        return CustomizedListviewRecent.newInstance(41);
    else if(position == 2)
        return CustomizedListviewMostRecents.newInstance(0);
    else if(position == 3)
        return CustomizedListviewPopulars.newInstance();
    else if(position == 4)
        return CustomizedListviewRecent.newInstance(42);
    else
        return CustomizedListviewRecent.newInstance(43);
}

这样做的常见原因是：

1. 人们认为这样做更有效率；或者
2. Fragment稍后可能需要参考。

对于（1），正如我所说，你不需要担心它（除非你想学习它并稍后调整，但现在就这样吧）。如果你需要（2），那么你可以这样做（最初见这里）。